A coating conveying chain is widely used in assembly line conveying equipment. It is non-standard equipment. A customer can customize it according to process requirements. A chain production line mainly consists of three parts: a conveying frame serving as a main body portion, a chain serving as a conveying carrier, and a power plant for providing power to operation of the equipment. With the advancement of science and technology and industrial production, a conveying chain technology has achieved rapid development in various fields such as wheel hubs and auto parts. In an actual production process of the wheel hubs, since the sizes and weights of on-site produced wheel types are varied, a load of a chain of a spray coating line dynamically changes with the switching of the wheel types. With the accumulation of years of production, the conveying chain will extend in different degrees. In addition, when the load of the conveying chain changes, especially when the weight of the load increases, the conveying chain is pressed and sunken, which may cause slack of the conveying chain or even folds on the chain and thus affect the conveying smoothness of the conveying chain, and may even cause serious problems such as jamming and breakage of the conveying chain and stop the entire conveying chain. Therefore, it is necessary to design a conveying apparatus to solve the negative impact on the conveying chain due to the extending of the conveying chain and a change in the load on the conveying chain.